Accessory carpal bone fracture

These fractures are sprain-avulsion type injuries caused by carpal hyperextension during racing. Carpal pain may be present.

Achondroplasia

Achondroplastic breeds are specifically bred for this condition. They have short maxillae, flared metaphyses and short, bowed limbs. This is accepted as part of the breed standard.

Alaskan Malamute chondrodysplasia

This condition leads to short limbs with bowed front legs and laterally deviated paws. Haemo-lytic anaemia is often also seen.

Angular deformity of tibia

In this condition, distal tibial growth plate injury or premature closure of the lateral aspect results in tarsal valgus.

Arthropathy associated with Scottish Fold cats

This condition has recently been characterised as an osteochondrodysplasia associated with inadequate cartilage maturation. A radiographic survey showed that all Scottish Fold cats examined were affected, whether or not they were symptomatic.

Avulsion of the tibial tuberosity

This is a fracture of the growth plate, which is seen more commonly in dogs with large quadriceps muscles.

Bilateral radial agenesis

In this inherited condition, the radius is partially or completely absent, and the ulna is shorter and thicker.

Bone cysts

These are benign, uncommon cystic lesions. Intramedullary metaphyseal haemorrhage may be involved. They are often asymptomatic, but may enlarge to cause pain or even pathological fracture.

Brachyury

Dogs of breeds with normally long tails occasionally develop with short tails. This is known as brachyury.

Bull Terrier osteochondrodysplasia

This condition leads to an abnormal gait with possible femoral neck fractures. Some long bones are distorted.

Burmese head defect

This congenital defect is inherited and has been described as autosomal recessive or autosomal dominant with incomplete penetrance. Hetero-zygotes have a range of facial dimensions. The condition is fatal to homozygotes. It is seen in the eastern, ‘new look’ or contemporary strain of Burmese. The upper maxillary region is duplicated.

Calcaneoquartal subluxation due to plantar tarsal ligament rupture

This is a common condition in athletic dogs, usually occurring in racing, but can also occur without a history of trauma in middle-aged pet dogs. The condition may be bilateral.

Calcaneus fracture

Extreme tension on the plantar side of the calcaneus or central tarsal bone fracture lead to calcaneal fractures, particularly in racing dogs. The right is usually affected due to the stresses generated while cornering left.

Carpal ligament weakening

Gradual degeneration and subsequent weakening of the carpal ligaments leads to subluxation and luxation of the carpus. The tarsus is also sometimes involved. Obesity predisposes, so weight loss is recommended.

Carpal soft-tissue injury

Soft-tissue injuries of the carpus are common in working dogs. Collateral ligament injuries, hyperextension injuries and luxations can be involved.

Cartilaginous exostosis

Osteochondromatous outgrowths from the long bones, scapula, ilium, vertebrae and phalanges can be seen radiographically in this condition.

Central core myopathy

This very rare condition leads to signs of muscle weakness which becomes progressively more severe. The reported cases were euthanased before two years of age.

Central tarsal bone fracture

This fracture is very uncommon in non-athletic dogs, but is common in racing Greyhounds. The fracture usually involves an avulsion of the plantar process. There are usually other tarsal bone fractures associated.

Chronic sesamoid disease

Chronic sesamoiditis may be an incidental finding on radiographs or a cause of lameness. Clinical signs include a gradual onset of lameness in one or both forelimbs.

Cleft palate/lip

This congenital condition involves a variety of possible defects including a unilateral cleft lip, incomplete fusion of the soft palate or an oronasal fistula.

Congenital elbow luxation

This condition is uncommon. There are two recognised types: type I is more severe and results in a 90° outward rotation of the proximal ulna. Lateral deviation of the antebrachium is seen, with marked reduction in elbow extension. The cause is unknown. Diagnosis is by radiography. Closed reduction is the treatment of choice, but some cases require open reduction. In type II luxation, the proximal radius is displaced caudolaterally. This type is less severe than type I. Some animals require no treatment, while others may require surgery, such as osteotomy of the radius or ulna.

Congenital scapulohumeral luxation

This is a rare condition, usually occurring at an early age, but may be a sequel to minor trauma in an adult. The deviation is usually medial, and craniocaudal radiographs will confirm this.

Cranial cruciate ligament rupture

This common injury often presents as a severe, acute onset lameness. Diagnosis is by ascertaining the presence of a ‘cranial drawer’ motion in the stifle, by radiography and by arthroscopy or arthrotomy.

Craniomandibular osteopathy

This condition is inherited in some breeds, but other factors may be important in others. Clinical signs include mandibular swelling, drooling and pain on opening the mouth. Irregular bone proliferation is seen on radiographs. The disorder is usually self-limiting, although in some cases hemimandibulectomy may be necessary.

Delayed/non-union of fractures of the distal third of the radius and ulna in Miniature and Toy breeds

There is a disproportionately high incidence of malunion following repair of fractures of the distal third of the radial and ulnar diaphyses. Inadequate immobilisation, infection and an easily disrupted blood supply to the bones may be responsible. Rigid fixation with plates or external fixators help reduce the risk.

Elbow dysplasia

Genetics and rapid growth predispose to this complex of diseases which include an ununited anconeal process, medial coronoid process disease and osteochondritis dissecans of the medial humeral condyle. It may be that elbow dysplasia is caused by osteochondrosis, possibly relating to incongruities of the trochlear notch. In the UK and USA there are screening schemes for elbow dysplasia in operation.

English Pointer enchondrodystrophy

This condition leads to short limbs and bowed front legs, with an abnormal gait.

Enostosis

Also known as panoesteitis or eosinophilic panosteitis. This condition is fairly common, affecting young dogs aged 6-18 months. Acute intermittent lameness affecting one or more limbs is seen, often associated with pyrexia. A viral aetiology is suspected. The condition is usually self-limiting.

Exertional myopathy

Precipitated by over-exertion in unfit dogs or in hot and humid conditions, this condition has a variable severity. Hyperacute cases show severe pain leading to myoglobinuria, acute renal failure and death, whereas acute cases have a lower mortality. A non-fatal subacute form is also seen.

Renal failure, associated with amyloidosis and swollen joints, is found in this condition. Hypergammaglobulinaemia and raised serum levels of interleukin-6 are seen.

Fibrotic myopathy of semitendinosus muscle

This condition is seen in young to middle-aged dogs. A fibrous band of tissue develops in the semitendinosus muscle, leading to a reduced ability to extend the affected limb. This condition may be part of a complex with Gracilis contracture.

Foramen magnum dysplasia

This condition involves a malformation of the occipital bone and enlargement of the foramen magnum. There may be concurrent hydro-cephalus and exposure of the brain stem and cerebellum. See also Hydrocephalus under Neurological conditions.

Gastrocnemius tendon avulsion

The gastrocnemius tendon becomes avulsed from the calcaneus, leading to an acute lameness or a chronic lameness with thickened tendons.

Gracilis contracture

This is usually seen in athletic dogs and leads to a gait alteration. This condition may be part of a complex with Fibrotic myopathy of semitendinosus. Surgery can help but the condition can recur.

Hemivertebrae

These abnormal vertebrae are wedge-shaped and are often associated with angulation of the spine. See also under Neurological conditions.

Hereditary canine spinal muscular atrophy

This condition is a motor neurone disease. Homozygotes for the condition have an accelerated form of the disease, whereas heterozygotes have an intermediate or chronic form. Dogs are usually affected at less than one year of age.

Hereditary myopathy of Devon Rex

This hereditary disease leads to clinical signs of generalised muscle weakness, collapse on exercise, ventroflexion of the neck and sometimes death from laryngospasm, possibly due to oropharyngeal weakness.

Hip dysplasia (HD)

This very common condition occurs in a wide range of breeds. Various deformities in the hip lead to joint instability with the development of degenerative joint disease. Genetics undoubtedly play a role, but environmental factors, such as nutrition and exercise, are also important. Various screening programmes are used around the world to attempt to reduce the incidence of this condition. Estimates of heritability vary from 20-60%, depending on breed, population examined and methods applied. Note that, for the purposes of this text, only the top 20 breeds for HD, as scored by the British Veterinary Association/Kennel Club Hip Dysplasia Scheme, have been included. However, this is potentially misleading, as variable numbers have been scored, and there is some inherent bias in the scheme in that some vets do not send the worst X-rays for scoring. More information can be obtained from the British Veterinary Association.

Hypokalaemic myopathy

Clinical signs of this condition include ven-troflexion of the neck and transient weakness. There may also be a tremor. Serum potassium levels of less than 3 mmol/1 are seen.

Idiopathic polyarthritis

Pain in more than one joint often suggests an immune-mediated polyarthritis. Canine idiopathic polyarthritis is the most common form of immune-mediated arthropathy. Approximately 25% of cases are associated with chronic infection remote from the joint, 15% are associated with gastrointestinal disease and another subset is associated with neoplasia remote from the joints. In the other cases, which account for about 50%, there is no other pathology or underlying aetiology detected.

Incomplete ossification of the humeral condyle

This condition may present with a history of mild intermittent lameness which is unre-ponsive to anti-inflammatory drugs. Acute severe lameness may follow exercise or mild trauma, corresponding with a humeral condylar fracture.

Increased anteversion of the femoral head and neck

This is associated with gait abnormalities, joint laxity and pain. It is a component of hip dysplasia.

Inguinal/scrotal herniation

Females are over-represented in this common condition. An inguinal mass or swelling is usually seen, although occasionally gastrointestinal signs are present.

Irish Setter hypochondroplasia

The limbs are slightly shortened in this condition. The ulna and radius may be bowed and carpal valgus is seen.

Juvenile onset distal myopathy

This recently recognised condition has been reported in several pups and has been described as a muscular dystrophy. Clinical signs include decreased activity and various postural abnormalities.

Labrador Retriever myopathy

This is an uncommon condition, but is widespread throughout the UK. Clinical signs include generalised muscle weakness, exercise intolerance and muscle wasting. Black- and yellow-coated Labradors are affected, and the condition is more common in working lines.

Lateral patellar luxation

Also known as genu valgum. This condition is often seen in the same breeds that are affected by hip dysplasia. There may be a genetic pattern of occurrence. Both stifles are often affected, causing a knock-kneed stance from five to six months of age.

Lateral torsion and tarsal valgus deformity

This condition is untreatable but rarely causes a clinical problem, being mainly a cosmetic fault.

Legg-Calve-Perthe’s disease

This condition involves an aseptic, avascular necrosis of the femoral head. Signs are usually seen from five months of age. Ischaemia of the femoral head leads to degeneration of the bone which presents as a progressive uni- or bilateral hind-limb lameness.

Lumbosacral disease

Inefficient facet geometry at the lumbosacral junction leads to an increase in osteophyte formation. This can be associated with a risk of lumbosacral stenosis.

Masticatory myopathy

Also known as eosinophilic myositis, masticatory myositis. This is a common condition and demonstrates acute and chronic forms. The acute disease presents with swelling of the masticatory muscles and trismus. The chronic form demonstrates atrophy of the masticatory muscles, with histology showing marked muscle fibrosis. The condition is immune mediated.

Medial coronoid process disease

This common condition is part of the osteo-chondrosis complex which affects the elbow. Fragmentation of the medial coronoid process occurs, with the fragments usually remaining attached to the annular ligament. Degenerative joint disease usually ensues. Signs of lameness are seen from four to five months of age.

Medial displacement of biceps brachii tendon

A gradual onset in lameness which is exacerbated by exercise is seen with this unusual condition. Palpation and manipulation of the shoulder can reveal pain, crepitus and sometimes a palpable popping of the tendon out of the intertubercular groove.

Medial patellar luxation

This condition usually presents as an intermittent lameness, although in bilateral cases it may present as a hind-limb gait abnormality. It is usually seen from six months of age, although in some cases may not cause clinical signs until the animal is older.

Mitochondrial myopathy

A defect in mitochondrial function leads to decreased exercise tolerance with tachycardia and tachypnoea resulting from severe acidosis. This condition can occasionally cause sudden death.

Mucopolysaccharidosis

This group of conditions results from inherited chromosomal abnormalities and leads to a metabolic bone disease. Type I disease causes a large broad head which may be associated with ocular and cardiac abnormalities. Pectus excavatum, fusion of the cervical vertebrae and hip subluxations also occur. Type VI disease causes dwarfism and skeletal, neurological and retinal abnormalities. There is no treatment, although some affected animals may have an acceptable quality of life.

Multiple enchondromatosis

This inherited condition leads to short bowed limbs with distorted diaphyses. Femoral neck fractures are seen, and the sternum lacks bone.

Multiple epiphyseal dysplasia

This inherited condition leads to short limbs, enlarged joints, hip dysplasia and osteoarthropathy in adults.

Muscular dystrophy

A sex-linked muscular dystrophy of Golden Retriever’s found in the USA has been found to be similar to Duchenne’s muscular dystrophy of humans. Clinical signs include exercise intolerance, gait abnormalities, trismus and occasionally cardiac involvement. Creatinine kinase (CK) is massively elevated on biochemistry. Other muscular dystrophies in dogs include the facioscapulohumeral type in Springers, which is associated with persistent atrial standstill. A condition resembling oculopharyngeal muscular dystrophy of humans has been reported in Bouviers.

Myasthenia gravis

See under Neurological conditions.

Myopathy associated with falling Cavalier King Charles Spaniels

Episodic collapse, often associated with exercise or excitement may be due to ultrastructural changes in the affected dog’s myocytes, but the exact cause is currently unclear. See also Episodic collapse under Neurological conditions.

Myotonia

Clinical signs of this condition include excess muscle mass, stiff gait after rest and collapse. Dyspnoea may be seen if the respiratory muscles are involved.

Ocular-skeletal dysplasia

This condition is inherited as an autosomal recessive, and causes clinical signs of shortened limbs and deviated joints, associated with ocular signs such as cataracts and retinal detachment. See also Retinal dysplasia with skeletal defects under Ocular conditions.

Odontoid process dysplasia

This condition results in atlantoaxial subluxation causing signs ranging from neck pain to quadraplegia. See also Atlantoaxial subluxation under Neurological conditions.

Osteochondrosis

Osteochondrosis is characterised by abnormal development of the cartilage in the physeal and epiphyseal sites. Common regions for osteochondrosis are the caudal humeral head, the medial condyle of the humerus, the medial cor-onoid process of the ulna, the anconeal process of the elbow, the lateral and medial condyles of the stifle and the medial ridge of the talus.

Osteogenesis imperfecta

This group of inherited diseases causes osteopaenia and increased bone fragility. The underlying defect is probably in collagen formation. The condition is rare, and the exact mode of inheritance is unknown. Cases may present with a history of multiple fractures with little or no trauma.

Osteosarcoma

This malignant tumour tends to affect the metaphyses of long bones, although they may also be seen in the axial skeleton. Rapid bone growth during early development, particularly in large- and giant-breed dogs may be involved in the aetiology, but a genetic predisposition is also suspected in some breeds. See also Neoplastic conditions.

Patellar luxation

Luxation of the patella can be due to abnormalities of the patellar groove or of the position of the tibial crest. It can cause chronic or intermittent lameness.

Patellar pain

This condition may be associated with patellar luxation, even after surgery, or may occur in the absence of luxation. Pain is seen on pressing the patella into the trochlear groove.

Perineal hernia

This relatively common condition presents as a swelling in the perineal region or as a defect palpable per rectum. Urinary bladder retroflexion with associated metabolic complications is seen in 20% of dogs.

Pes varus

This is seen at five to six months of age, and is probably related to an underlying tibial dysplasia.

Plasmacytic-lymphocytic gonitis

This condition of unknown aetiology leads to joint laxity and instability and is seen in up to 10% of dogs undergoing surgery of the cranial cruciate ligament.

Polyarthritis/meningitis

The underlying disorder in this condition is an idiopathic polyarteritis, which may be becoming more common. The main clinical signs are related to meningitis, such as neck pain and fever, but joint inflammation is not unusual. The severity of the disease varies with breed. Milder forms are often self-limiting, but the more severe forms may not be.

Polydactyly/syndactyly

Several breeds show a tendency to more than the normal number of digits (polydactyly) or fused digits (syndactyly). Often these abnormalities do not cause a clinical problem.

Prognathia

Overshot jaw.

Pseudoachondrodysplasia

This condition leads to short, bent limb bones and short vertebrae. Osteopaenia may be seen.

Pyruvate kinase deficiency

As well as haematological abnormalities, this inherited condition can lead to intramedullary osteosclerosis.

Retrognathia

Undershot jaw.

Sacrocaudal dysgenesis

See under Neurological conditions.

Scottish Fold arthropathy

Scottish Fold cats have abnormally shaped ears, due to an abnormality in the ear cartilage (inherited as a simple autosomal dominant). Homozygotes for this defect can develop generalised cartilage defects causing a shortening and thickening of the bones of the limbs, tail and spine and a progressive arthropathy.

Shoulder luxation

This condition usually occurs at three to four months. Flexed and rotated views of the shoulders can reveal the abnormality on radiography.

Spondylosis deformans

Also known as ankylosing spondylitis. Bony spurs (osteophytes) form around the margins of the vertebral endplates. They become more common with age, and are often apparent radiographically, but are rarely of clinical significance.

Spontaneous tibial fracture

Spontaneous fractures of the caudal distal articular margin of the tibia have been reported in racing Greyhounds, often associated with malleolar fractures. Degenerative joint disease is a common sequel, so prognosis after internal fixation is guarded.

Superficial digital flexor tendon luxation

This uncommon condition causes acute but moderate lameness. A calcaneal bursal effusion is seen. The luxation is usually lateral.

Temporomandibular dysplasia/luxation

Abnormal development of the articular surfaces leads to temporomandibular dysplasia with laxity of the joint. The condition can be seen from six months of age. Clinical signs include open mouth locking, often associated with yawning, and luxation which may be chronic. Degenerative joint disease and masticatory muscle wastage may be seen in chronic cases.

Transitional lumbosacral vertebra

This anomaly is characterised by separation of the first sacral segment identified on the lateral view of a radiograph by the presence of a rad-iolucent disc space between what are normally the first and second sacral segments. On the ventrodorsal view, there is separation of the spinous processes between what are normally the first and second sacral segments. The sacroiliac attachment is often weakened, leading to premature disc degeneration. Together with spinal canal stenosis, this can lead to cauda equina syndrome.

Umbilical hernia

In this condition, the umbilical ring fails to close at birth, and as abdominal pressure increases with age, abdominal fat and even intestines can be forced through. Many of these cases require surgical repair.

Ununited anconeal process

In German Shepherd Dogs the anconeal process develops as a separate centre of ossification, which should be fused to the ulna by twenty weeks. Failure of fusion leads to an ununited anconeal process which is part of the elbow osteochondrosis complex. Degenerative joint disease often occurs, leading to a lameness which is seen from four to five months of age.

Vaccine-associated vasculitis with hypertrophic osteopathy

This vasculitis, which is associated with routine vaccinations, leads to initial gastrointestinal signs, which later develop into lameness and hypertrophic osteodystrophy.

Von Willebrand heterotopic osteochondrofibrosis

In this condition a mass of bony, fibrous or cartilaginous tissue develops near the hip muscles. A severe lameness can result, which is mainly mechanical in nature.